The bridging of gaps or other passages between two raised edges by so-called heavy vehicles requires crossing structures which are not only adapted for rapid laying, but are also a light, making it easier for them to be transported and put to use.
These requirements of lightness and easy handling conflict with the properties of sturdiness, mechanical strength and bending resistance required in view of the weight of the vehicles which may use these crossing structures.
These crossing structures are generally either, of the scissor type or simple crossing structures in the form of a plurality of sections which can butt against one another.
The scissor-type crossing structures comprise two or three inseparable elements which are extended by rotation in a vertical plane about the common axis of the two elements.
After deployment, these crossing structures can be laid either by means of a jib or with the aid of a manipulator.
The main disadvantage of scissor-type crossing structures is that, during deployment or laying, the entire crossing structure is cantilevered in relation to the carrier vehicle, thus making it necessary to limit the weight of the crossing structures and therefore causing a limitation in their length and consequently that of the gaps which can be bridged.
Moreover, during deployment or laying, the crossing structure rises to such a height that it can easily be detected by enemy observation facilities. On the other hand, the jointing and deployment system makes the assembly as a whole considerably heavier, this making it necessary to limit its reach because the forces on the cantilevered deployment system become too great.
In the case of a simple crossing structure, the sections are transported superposed on one another and then deployed in translational motion by a manipulator which also serves for laying the structure.
With this type of crossing structure, however, the sections have to be centered, assembled and locked with one another before being laid.
To date, the sections have been assembled together by means of centering and connecting members formed, for example, by bolts or keys or mechanical assemblies comprising a device with a rack and with a pawl actuated by a pusher.
The centering and connecting members employed are often complicated to use because of the dimensions of the sections, thus making it necessary for several crew members to be present outside the vehicle for controlling and guiding the maneuvers.
This need considerably restricts the use of such crossing structures, because it prevents them from being used in a contaminated atmosphere, such as may be encountered during nuclear, bacteriological or chemical warfare.